MP Dominic Grieve is showing no sign of stepping back from high-profile politics after losing his Attorney General post with an attack on Boris Johnson’s ‘draconian’ ideas on terrorism.

The Beaconsfield MP, who also represents Marlow, stood up to the Mayor of London, who said Britons leaving unannounced for Syria should be presumed in law to be terrorists.

But the lawyer slammed his fellow Conservative for calling for changes in the law to control people’s movement, saying there were "perfectly innocent reasons" for people to visit Syria.

Mr Grieve told the BBC: "It is a draconian proposal because it would envisage getting rid of ordinary principles of common law which would put the burden on the prosecution to prove its case.

"Boris Johnson is suggesting that effectively there should be rebuttable presumption, so that the moment it was established by a prosecutor that you had gone to a country like Syria the burden would be on you to show that you were acting innocently.

"As you could imagine there are going to be people who have perfectly innocent reasons for going to Syria, from seeing their families to taking medical aid, quite legitimately."

Mr Johnson, who will stand as MP for Uxbridge in next year’s general election, called for the tighter controls in his column for the Daily Telegraph.

And he said the authorities should be given more powers to monitor those returning from war-torn countries like Syria.

Last week, a militant - believed to be British - was filmed killing American journalist James Foley.

More than 500 Britons are believed to have joined the group Islamic State (IS), which is fighting to capture large parts of Iraq and Syria.